Crops such as citrus, peaches, bananas and mangoes often become biologically contaminated post-harvest. Contamination can be initiated pre-harvest (eg. by parasitic presence at the time of picking/harvesting), during harvesting (eg. where contaminants are introduced by mechanical harvesters or human intervention) and post-harvest (eg. where parasites and spore settle on post-harvested produce).
Regardless of the time of contamination, it is desirable to treat harvested fruit, vegetables and plants prior to transportation and storage to eradicate any such contamination. For example, international quarantine regulations and inspection require fruit to be free of live pests. To this extent, post-harvest broad spectrum pesticides are currently applied to post-harvest produce, but there are international concerns with the residues of such pesticides on the fruit and vegetables so treated, especially the effects of such residues on humans.